The goal of the Transgenic Animal Core is to assist the investigators of each project with the design, production, characterization, and maintenance of genetically modified mice. To achieve this goal, the core will perform the following functions. First, the core will design and construct transgenes and develop genotyping assays and purify transgene DNA for microinjection. Second, the core will generate transgenic founders via microinjection of transgene DNA into fertilized eggs from the C57BL/6 strain of mice. Potentially transgenic offspring will be identified using genotyping assays developed by the core. Founder mice will be characterized for the ability to transmit the transgene to offspring. The number of independent chromosomal integration sites in each founder will be determined. Germline-competent mice, each with a transgene integrated at a single genomic locus, will be delivered to project leaders. The third service of thecore will be to design and facilitate production of gene-targeted mice. Specifically, the core will produce and purify the gene-targeting constructs and test embryonic stem (ES) cell screening assays. The core will then work with an off-site ES cell facility to introduce the DNA into ES cells and isolate appropriately targeted ES cell clones. Appropriately targeted clones will then be used for blastocyst injections. Chimeric mice will be sent to UAMS and the core will identify those with the ability to produce offspring harboring the targeted allele. Germline-competent mice will then be delivered to project leaders. Finally, the core will assist in the characterization, maintenance, and preservation of genetically-modified mice. Quantitative reversetranscriptase polymerase chain reaction (RT-PCR) assays will be designed to specifically detect transgene mRNA and then used to determine the tissue distribution of transgene mRNA expression. Expression patterns of each Cre-deleter strain will be verified by crossing with R26R Cre-reporter mice. Each new mouse model generated by the core, or imported for use by the program, will be cryo-preserved via sperm cryopreservation for long-term bio-security, cost-reduction, and efficient access.